The present invention relates to a new and improved construction of a roller apron or strand guide arrangement for a continuous casting plant or installation, especially for casting steel, for supporting a partially solidified casting or strand, which roller apron is of the type comprising a number of roll pairs which follow one another in succession in the direction of strand travel, the bearings of at least one roll being arranged upon a crosshead or traverse extending essentially parallel to the lengthwise axes of the rolls. This traverse can be placed against stops or impact members which govern the strand cross-sectional thickness or format and coacts at both of its ends with pivotable levers articulated at the machine frame and at a movement device.
During the continuous casting of steel strands, especially slabs, considerable demands are made of the strand guide rolls, bending rolls and driving rolls during the casting operation, as concerns strength, bending-through, resistance to temperature changes, wear and so forth. When disturbances arise, for instance metal break-out, as a general rule the slabs only can be conveyed out of the roller apron at an appreciably lower temperature and in an essentially solidified state. When this happens such rolls are frequently loaded beyond their contemplated load limit. Oftentimes what then happens is that such rolls bend or rupture.
In order to increase the operational time of continuous casting installations it is not uncommon to exchange strand guide elements and/or individual rolls during the course of the normal preventive maintenance work. It is of course particularly important that such maintenance work be carried out in the shortest amount of time. Furthermore, in the presence of a disturbance it is of significance to be able to exchange defective rolls as quickly as possible.
Now it is known to apply guide rolls, bending rolls and driving rolls hydraulically against the surface of the strand in the manner such that upon overloading of a roll by the strand such can deviate in a direction away from the strand. During the assembly and disassembly of such rolls, depending upon the construction of the roll framework, either the hydraulic cylinder coacting with the roll bearings must be removed together with the roll, or, pressure transmission elements which are connected with the traverse or crosshead carrying the rolls must be disconnected from such traverses. Both of the aforementioned constructions require complicated and as a general rule poorly accessible dismantling work. Moreover, hydraulic overload safety devices for strand guide rolls of slab casting machines of the prior art continuous casting plants generally require at least one respective hydraulic cylinder at each side of the strand and, thus, are associated with high fabrication costs of the installation.
There is also known to the art a roller apron framework where bearings of a number of rolls of a roller guide path, which rolls follow one another in succession in the direction of strand travel, are arranged upon traverses or crossheads extending parallel to the lengthwise axes of the rolls. Such traverses can be applied against stops or impact members which govern the thickness of the strand. At both of their ends these traverses or crossheads have support surfaces which cooperate with pivotable levers articulated to both sides of the frame. These pivotable levers, for the purpose of pivoting or rocking the same, are connected with movement devices in the form of spindles. With this equipment there should be prevented movement of the rolls during the casting operation in a direction transversely with respect to the guided strand surface. Furthermore, there are provided devices which do not transmit the forces acting from the strand upon the rolls to the movement devices. An overload protection is not provided for these rolls. Consequently, there cannot be eliminated undesirable bending of the rolls, roll rupture and destruction of the roll bearings due to overload.